The present invention is directed to methods and devices for implanting replacement cardiac valves. Replacement cardiac valves are implanted when the patient""s native valve exhibits abnormal anatomy and function due to congential or acquired valve disease. Congenital abnormalities can be tolerated for years only to develop into life-threatening problems later. Acquired valve disease may result from various causes such as rheumatic fever, degenerative disorders of the valve tissue, and bacterial or fungal infections.
Valve dysfunction can be classified as either stenosis, in which the valve does not open properly, or insufficiency, in which the valve does not close properly. Stenosis and insufficiency can occur at the same time and both abnormalities increase the workload on the heart in pumping blood through the body. The ability of the heart to function with the increased workload is a major factor in determining whether the valve should be replaced.
When the valve must be replaced using conventional methods, the patient must undergo an invasive, traumatic surgical procedure. The patient""s chest is opened with a median sternotomy or major thoracotomy to provide direct access to the heart through the large opening in the chest. The heart is then stopped and the patient is placed on cardiopulmonary bypass using catheters and cannulae inserted directly into the heart and great vessels. The heart, or a great vessel leading to the heart, is then cut open to access and remove the malfunctioning valve. After removing the valve, the replacement valve is then sewn into place. After the new valve has been implanted, the chest is then closed and the patient is weaned off cardiopulmonary bypass support.
The conventional open-chest surgery described above is problematic in that it is highly invasive, traumatic and requires a lengthy recovery time. These drawbacks to conventional open-chest surgery prevent some patients from undergoing a valve implantation procedure even though a new cardiac valve is needed.
U.S. Pat. Nos. 5,370,685, 5,411,552 and 5,718,725, which are hereby incorporated by reference, describe devices and methods for implanting a new cardiac valve without requiring a median sternotomy or major thoracotomy. Such devices and methods reduce the pain, trauma and recovery time as compared to conventional open-chest surgery.
An object of the present invention is to provide additional devices and methods which reduce the trauma associated with conventional open-chest methods and devices for implanting cardiac valves.
In accordance with the object of the invention, a system and method for implanting a cardiac valve is provided which does not require a median sternotomy or major thoracotomy. The devices and methods of the present invention are preferably carried out by passing the valve through a blood vessel, preferably the femoral artery, so that the median sternotomy or major thoracotomy is not required. Alternatively, the systems of the present invention also permit introduction of the valve through a small incision between the patient""s ribs without cutting the ribs or sternum.
In a first aspect of the invention, a valve displacer is used to hold the native valve leaflets open so that the native valve does not need to be removed. The valve displacer is preferably introduced into the patient in a collapsed condition and expanded to displace and hold the leaflets open. The valve displacer may either be expanded with an expansion mechanism, such as a balloon, or may be self-expanding. In a preferred embodiment, the valve displacer has a first end, a second end and a central section between the first and second ends. The first and second ends are preferably flared outwardly to form a circumferential recess around the central portion. The native leaflets are trapped within the recess when the valve displacer is deployed.
In another aspect of the invention, the valve is also introduced into the patient in a collapsed condition and expanded within the patient. The valve may either be expanded with an expansion mechanism, such as a balloon, or may be self-expanding. The cardiac valve may be coupled to the valve displacer or may be positioned independent from the valve displacer while still substantially performing the functions of the native valve. For instance, a replacement aortic valve may be positioned in the ascending or descending aorta to substantially perform the functions of the native aortic valve.
The cardiac valve is preferably delivered separate from the valve displacer but may also be integrated with the valve displacer during introduction and deployment. In a preferred embodiment, the valve has protrusions which engage openings in the valve displacer. In another embodiment, the valve has sharp elements or barbs which either pierce the native valve tissue or engage the sides of the openings in the valve displacer.
In yet another aspect of the present invention, the valve and valve displacer are preferably introduced into the patient with a catheter system. In a preferred system, the valve displacer is mounted to a first catheter and the valve is mounted to a second catheter which passes through and is slidably coupled to the first catheter. Alternatively, the valve displacer and valve may be mounted to a single catheter. The term catheter as used herein refers to any catheter, trocar or similar device for introducing medical devices into a patient.
In still another aspect of the present invention, the valve delivery catheter has a temporary valve mechanism which provides temporary valve functions after deployment of the valve displacer. The temporary valve mechanism prevents regurgitation while the native valve is held open and before deployment of the replacement cardiac valve. The temporary valve mechanism is preferably a balloon which is inflated and deflated as necessary to permit downstream flow and prevent retrograde flow. Although it is preferred to implant the cardiac valve while the patient""s heart is beating, the devices and methods of the present invention may also be used with the patient""s heart stopped and the patient supported by a bypass system.
These and other advantages and aspects of the invention will become evident from the following description of the preferred embodiments and claims.